Conventional mid-infrared focal plane arrays are based on the use of mercury-cadmium-telluride (HgCdTe) photodetectors. Alternatives to HgCdTe photodetectors are being developed which promise operation at higher temperatures with a detectivity comparable to or better than the HgCdTe photodetectors. Among these alternatives are photodetectors formed from antimonide-based type-II superlattices in which there is, at least theoretically, a promise of longer intrinsic carrier lifetimes due to the suppression of Auger recombination. Additionally, the antimonide-based type-II superlattices have a staggered band alignment which allows both the energy band structure and the energy bandgap of the superlattice to be tailored to enhance detector performance for the absorption of infrared light over a wide wavelength range of about 3 to 25 microns (μm) or more. The development of infrared focal plane arrays including devices using antimonide-based type-II superlattice photodetectors has been reviewed in an article by A. Rogalski entitled “Competitive Technologies for Third Generation Infrared Photon Detectors” in Proceedings of the Society of Photo-Optical Instrumentation Engineers (SPIE), vol. 6206, 62060S (2006). Another review of type-II superlattice photodetectors can be found in an article by G. J. Brown entitled “Type-II InAs/GaInSb Superlattices for Infrared Detection: an Overview” in Proceedings of the Society of Photo-Optical Instrumentation Engineers (SPIE), vol. 5783, pp. 65-77 (2005).
The present invention provides an advance over the art in the development of antimonide-based type-II superlattice photodetectors and photodetector arrays by providing devices which have a lateral conduction structure comprising a semiconductor p-n or p-i-n junction which is formed across the width of the photodetector instead of a more conventional vertical conduction structure in which the semiconductor junction is formed in an epitaxial growth direction (i.e. a vertical direction). The lateral conduction structure formed in the photodetectors of the present invention allows the semiconductor junction to be sandwiched between upper and lower cladding layers which passivates the semiconductor junction. This is advantageous to reduce surface recombination and thereby improve device performance.
Embodiments of the present invention can be used as multi-color photodetectors and photodetector arrays to detect light in two or more different wavelength bands. The use of a lateral conduction structure allows the different wavelength bands to be sensed simultaneously or independently. A bias electrode can also be provided in these embodiments of the present invention to vary a cut-off wavelength, or to control a depletion region width in the photodetectors and photodetector arrays.
These and other advantages of the present invention will become evident to those skilled in the art.